Cartilaginous Acetabular Index Research Articles

The role of the cartilaginous to osseous acetabular angle ratio in children with developmental dysplasia of the hip.

This study aims to demonstrate the use of the cartilaginous to osseous acetabular angle ratio (AAR) in surgical decision-making for hip dysplasia. Data were collected from patients who underwent an MRI of the hip after conservative treatment for developmental dysplasia of the hip between August 2019 and 2022. The data included demographic information as well as an anteroposterior pelvic radiograph. The osseous acetabular index (OAI) was measured using x-ray, while the cartilaginous acetabular index (CAI) and the cartilaginous acetabulum head index (CAHI) were measured using MRI. The square of the CAI to OAI, AAR, was calculated. The patients in the residual hip dysplasia (RHD) group were categorized as having an OAI above 20°. During the postoperative follow-up, we evaluated the patients in this group who underwent Bernese triple pelvic osteotomy. Data on surgical patients with an observation period that exceeded 1 year were collected and analyzed. The distribution of the AAR among the different groups was analyzed. A receiver operating characteristic (ROC) predictive model was constructed using the AAR of the patients in the normal and surgical groups to evaluate the need for surgery. It was found that there was a significant difference in the OAI, CAI, CAHI, and AAR between the RHD group (OAI 26.15 ± 3.90°, CAI 11.71 ± 4.70°, CAHI 79.75 ± 6.27%, and AAR 5.88 ± 4.24) and the control group patients (OAI 16.77 ± 5.39°, CAI 6.16 ± 3.13°, CAHI 85.05 ± 4.91%, and AAR 2.71 ± 2.08) (p < 0.001). A total of 93.5% of the control group patients had an AAR ≤5, while only 6.5% had an AAR >5. The results of postoperative imaging follow-up were "excellent" in 52 patients and "good" in 3, while the functional follow-up results were excellent in 53 and good in 2. In 15 patients, the observation period exceeded 1 year. The mean observation period was 633.1 ± 259.6 days and the preoperative CAHI was 71.7 ± 4.8%. Of the patients with an AAR >5, a substantial 94.8% (55/58) of them were reported to have undergone surgery, while all patients with an AAR less than or equal to 5 did not undergo surgery (91/91). Based on the ROC, a cutoff value of 5.09 was identified for the need for surgery in children with RHD. A surgical decision for residual hip dysplasia can be based on the AAR. An AAR >5 may be a potential indicator for surgical intervention in patients with RHD.

Hip Morphology on Post-Reduction MRI Predicts Residual Dysplasia 10 Years After Open or Closed Reduction.

There is limited evidence supporting the value of morphological parameters on post-reduction magnetic resonance imaging (MRI) to predict long-term residual acetabular dysplasia (RAD) after closed or open reduction for the treatment of developmental dysplasia of the hip (DDH). We performed a retrospective study of 42 patients (47 hips) undergoing open or closed reduction with a minimum 10 years of follow-up; 39 (83%) of the hips were in female patients, and the median age at reduction was 6.3 months (interquartile range [IQR], 3.3 to 8.9 months). RAD was defined as additional surgery with an acetabular index >2 standard deviations above the age- and sex-specific population-based mean value or Severin classification grade of >2 at last follow-up. Acetabular version and depth-width ratio, coronal and axial femoroacetabular distance, cartilaginous and osseous acetabular indices, transverse ligament thickness, and the thickness of the medial and lateral (limbus) acetabular cartilage were measured on post-reduction MRI. At the time of final follow-up, 24 (51%) of the hips had no RAD; 23 (49%) reached a failure end point at a median of 11.4 years (IQR, 7.6 to 15.4 years). Most post-reduction MRI measurements, with the exception of the cartilaginous acetabular index, revealed a significant distinction between the group with RAD and the group with no RAD when mean values were compared. The coronal femoroacetabular distance (area under the receiver operating characteristic curve [AUC], 0.95; 95% confidence interval [CI], 0.90 to 1.00), with a 5-mm cutoff, and limbus thickness (AUC, 0.91; 95% CI, 0.83 to 0.99), with a 4-mm cutoff, had the highest discriminatory ability. A 5-mm cutoff for the coronal femoroacetabular distance produced 96% sensitivity (95% CI, 78% to 100%), 83% specificity (95% CI, 63% to 95%), 85% positive predictive value (95% CI, 65% to 96%), and 95% negative predictive value (95% CI, 76% to 100%). A 4-mm cutoff for limbus thickness had 96% sensitivity (95% CI, 78% to 100%), 63% specificity (95% CI, 41% to 81%), 71% positive predictive value (95% CI, 52% to 86%), and 94% negative predictive value (95% CI, 70% to 100%). Coronal femoroacetabular distance, a quantitative metric assessing a reduction's concentricity, and limbus thickness, a quantitative metric assessing the acetabulum's cartilaginous component, help to predict hips that will have RAD in the long term after closed or open reduction. Diagnostic Level IV . See Instructions for Authors for a complete description of levels of evidence.

MRI May Be More Valuable than Pelvic Radiographs in the Assessment of Paediatric Borderline Acetabular Dysplasia.

The osseous acetabular index (OAI) and cartilaginous acetabular index (CAI) is often used in diagnosing acetabular dysplasia (AD) in children. We examined the reliability of OAI and CAI in AD diagnostics and compared OAI measurements obtained from radiographs versus MRI. Four raters performed retrospective repeated measurements of the OAI and CAI on pelvic radiographs and MRI scans of 16 consecutive patients (mean age 5 years (2-8)) examined for borderline AD during a period of 2½ years. In MRI, the image selected for analysis by the raters was also registered. Spearman's correlation, scatter plots, and Bland-Altman (BA) plots were analysed for correlation between OAI on pelvic radiographs (OAIR) and MRI scans (OAIMRI), while intra- and interrater reliability was assessed for OAIR, OAIMRI, CAI, and MRI image selection using intraclass correlation coefficients (ICC). ICC values for inter- and intrarater reliability of OAIR, OAIMRI, and CAI were all above 0.65, with no significant differences observed. ICC values (CI) for individual raters' MRI image selection was 0.99 (0.998-0.999). The mean difference (95% CI) between OAIR and OAIMRI was -0.99 degrees (-1.84; -0.16), while the mean absolute difference (95% CI) between OAIR and OAIMRI was 3.68 degrees (3.17; 4.20). Absolute differences between OAIR and OAIMRI was independent of pelvic positioning or time interval between radiographs and MRI scans. OAI and CAI had high Intrarater reliability but mediocre interrater reliability. There was an absolute difference of 3.7 degrees in OAI between pelvic radiographs and MRI scans.

Cartilaginous predictors of residual acetabular dysplasia (RAD) in developmental dysplasia of the hip following closed or open reduction: A systematic review and meta-analysis.

This study was designed to analyze the cartilaginous predictors of residual acetabular dysplasia (RAD) after early treatment of developmental dysplasia of the hip and their diagnostic accuracy. Databases such as PubMed, Embase, Cochrane, and Web of science were searched to screen the literature. The quality of the literature was assessed by the QUADAS-2 tool. Qualitative and quantitative synthesis of literature were performed based on extracted data. For quantitative synthesis studies, the sensitivity, specificity, diagnostic odds ratio (DOR), and summary receiver operating characteristic (SROC) curve with corresponding confidence intervals were calculated. For the cartilaginous acetabular index (CAI) group, the combined values of sensitivity, specificity, and DOR were 0.80 (95% CI = 0.54-0.93), 0.73 (95% CI = 0.57-0.84), and 10.62 (95% CI = 3.96-28.53), respectively. The corresponding values in the cartilaginous center-edge angle (CCE) group were 0.71 (95% CI = 0.57-0.82), 0.78 (95% CI = 0.66-0.87), and 8.64 (95% CI = 3.08-24.25), respectively. The area under the curve (AUC) of SROC was 0.82 (95% CI = 0.78-0.85) and 0.80 (95% CI = 0.76-0.83) for the CAI and CCE groups. The CAI group had higher sensitivity, DOR, and AUC than the CCE group. Both of these two groups have good diagnostic accuracy, and CAI/L-AI has a little edge over CCE/L-CEA. However, there is still more research needed to determine whether they can be used as independent indications for secondary orthopedic surgery.Systematic review registration: [https://www.crd.york.ac.uk/PROSPERO/], identifier: [CRD42022338332].

Management and effects of residual limbus inversion following closed reduction in developmental hip dysplasia: Protocol for a multicenter randomized controlled trial.

Closed reduction is a common treatment method for developmental dysplasia of the hip (DDH) in children aged 6-18 months. Residual acetabular dysplasia (RAD) is the most common complication associated with closed reduction. Residual limbus inversion (RLI) is a common condition following DDH closed reduction. Previously, we confirmed that when limbus inversion exceeds 32.2% of the acetabular depth after closed reduction, RLI persists and leads to RAD; however, this was based on a small cohort with a short-term follow-up period. The long-term fate of RLI and the correlation between RLI and RAD have yet to be verified. Therefore, this multicenter clinical study protocol was designed in three parts to investigate the effect of RLI on acetabular development after closed reduction of DDH (a multicenter retrospective cohort study), effect of RLI clearance on acetabular development (a multicenter retrospective and prospective randomized controlled study), and influence of inverted limbus clearance on acetabular development during DDH reduction (a multicenter prospective cohort study). Statistical analysis was performed by assessing the basic measures of acetabular development including the acetabular index and central-edge angle using frontal pelvic radiographs; the magnitude of limbus inversion, cartilaginous acetabular index, and T1ρ mapping values were measured using magnetic resonance imaging. The multicenter retrospective cohort studies required 5 years of follow-up period at minimum, and the prospective randomized controlled studies required reviews of frontal pelvic radiographs every 6 months as well as data pooling every 2 years to compare the short- and mid-term outcomes of hip joint morphological development between the two groups of pediatric patients. This research program is expected to verify that RLI following closed reduction of DDH can affect acetabular development and that limbus excision during DDH reduction can improve postoperative RAD. Therefore, the indication and timing of surgical intervention for RLI after closed reduction of DDH provide a basis for revising the acceptable criteria for utilizing closed reduction of DDH to reduce the incidence of osteoarthritis caused by RAD following DDH treatment. Clinical Trial: http://www.chictr.org.cn/showproj.aspx?proj=35045 (ChiCTR1900020996).

Intra- and interobserver variability of novel magnetic resonance imaging parameters for hip screening and treatment outcomes at age 5years.

The outcome measure of neonatal hip screening is usually the radiographic acetabular index. To assess the feasibility of magnetic resonance imaging (MRI) without sedation and compare the utility of outcome parameters measured from MRI images. The invitation for MRI scanning at 5years of age was incorporated into follow-up for babies who had more than one ultrasound examination during treatment or surveillance. Diagnostic images were obtained in 132 of 134 children. The mean osseous acetabular index (standard deviation [SD]) was 16.6 (3.3) degrees for the right hip and 17.8 (3.2) for the left; the values for the cartilaginous acetabular index were 3.1 (3) and 3.4 (3.2). The mean downslope of a tangent to the lateral bony acetabular roof was 10.4 (4.5) and 9.0 (4.3) with respect to Hilgenreiner's line and that of a line drawn through the apex to the margin of the acetabulum was 3.7 (4.6) and 3.9 (4.7). Intra- and interobserver variation was greater for measures specific to the lateral acetabular roof than for ossific and cartilaginous indices. There was significant negative correlation between the downslope of the tangent to the lateral roof index and the age at onset of treatment on both sides, but no significant correlation for ossific or cartilaginous acetabular indices or apex-marginal index. MRI without sedation at 5years of age is feasible as an outcome measure for hip screening programmes. Parameters specific to the lateral acetabulum may better reflect acetabular sufficiency, despite having greater observer variation than cartilaginous and ossific acetabular indices.

A Preliminary Cadaveric MRI Study of Fetal Hip Development.

PurposeThe earlier the detection of the hip joint is discovered, the better the final result. The purpose of this study aimed to investigate the fetal hip development using magnetic resonance imaging (MRI), so as to alert clinicians to possible abnormal development during intrauterine life.MethodMeasurements of 34 cadaver fetuses (68 hips) were obtained regarding acetabular width and depth, anterior bony acetabular index (ABAI), anterior cartilaginous acetabular index (ACAI), posterior bony acetabular index (PBAI), and posterior cartilaginous acetabular index (PCAI). The standard values of each acetabular measurement index were obtained, and the gestational age-measurement index change trend chart was drawn to comprehensively analyze the normal development law of the fetal hip joint.ResultsWith the development of fetuses, the width and depth of acetabular increase linearly, and the slope of acetabular width was larger than that of depth. In addition, two change points during the 24th and 34th weeks of gestation were detected with regard to width. ABAI and PBAI also decreased. ABAI demonstrated an approximately linear trend, while PBAI shows a non-linear trend. During the 36th week, the change point in PBAI was observed. ACAI and PCAI exhibited slow increases, indicating a non-linear trend. During the 21st and 36th weeks of gestation, the change points regarding ACAI were observed. During the 22nd week of gestation, the change point for PCAI was observed.ConclusionPlots of the parameters obtained via MRI examinations of cadaver fetuses across gestational age comprehensively illustrated the fetal hip development. This developmental information about the hip joint has the potential to guide clinicians in the early detection of abnormal hip joint development during intrauterine life.

MRI Predictors of Residual Dysplasia in Developmental Dysplasia of the Hip Following Open and Closed Reduction.

Following open or closed reduction for children with developmental dysplasia of the hip, there remains a significant risk of residual acetabular dysplasia which can compromise the long-term health of the hip joint. The purpose of this study was to use postoperative in-spica magnetic resonance imaging (MRI) data to determine factors predictive of residual acetabular dysplasia at short-term follow-up. We retrospectively reviewed 63 hips in 48 patients which underwent closed or open reduction and spica casting for developmental dysplasia of the hip. MRI performed in-spica at ∼3-week follow-up were used to assess 11 validated metrics and 2 subjective factors. Acetabular index (AI) was measured on anteroposterior pelvic radiographs at 2-year postoperative follow-up. Binary logistic regression was then used to identify variables predictive of residual dysplasia, defined as an AI greater than the 90th percentile for age based on historic normative data. Average age at surgical reduction was 9.3±3.2 months. 58.7% (37/63) of reductions were open. A total of 43 (68.3%) hips demonstrated residual acetabular dysplasia at 2 years postoperatively based on normative values. In those with persistent dysplasia, patients were on average older at the time of reduction (10.0 mo±3.2 vs. 8.0 mo±2.8, P=0.010) and more likely female (88.4% vs. 60.0%, P=0.010). Patients with residual dysplasia were more likely to have mild subluxation on postoperative MRI (40.0% vs. 10.5%, P=0.022). Hips with a cartilaginous acetabular index (CAI) of >23 degrees were 7.6 times more likely to develop residual dysplasia. Type of reduction (ie, closed vs. open) did not appear to influence the rate of residual dysplasia (P=0.682). In this series, the rate of residual dysplasia after surgical reduction was higher than most previous reports, with no appreciable difference between closed and open reductions. Older age, female sex, and a higher CAI were associated with a greater risk of persistent radiographic dysplasia. In particular, hips with a CAI >23 degrees were 7.6 times more likely to be dysplastic at 2-year follow-up. Level III.

The fate of inverted limbus in children with developmental dysplasia of the hip: Clinical observation.

In this study, we observed the fate of the inverted limbus after closed reduction for the treatment of developmental dysplasia of the hip (DDH) and its impact on acetabular development. Clinical data were reviewed for 26 DDH patients with an inverted or overriding limbus after closed reduction for hip dysplasia. Patients were divided into a residual inversion group (19 cases, 22 hips) and a spontaneous resolution group (7 cases, 7 hips) according to the limbus status at the last follow-up. Differences in the osseous acetabular index (AI) and cartilaginous AI (CAI), the magnitude of limbus inversion, center-edge angle (CEA), height-to-width index (HWI) of the femoral head epiphysis, and avascular necrosis (AVN) at last follow-up were compared. There were no statistically significant differences in the preoperative AI and CAI between groups. The magnitude of limbus inversion after reduction and the AI at the final follow-up in the residual inversion group were both larger than those in the spontaneous resolution group. The CAI, CEA, and HWI were not significantly different between groups. The magnitude of limbus inversion in the residual inversion group did not significantly decrease over time. AVN occurred in five hips in the residual inversion group. No cases of AVN occurred in the spontaneous resolution group. After closed reduction, the inverted limbus was not absorbed in the majority of cases; instead, it evolved into a thin layer of fibrous tissue embedded between the femoral head and acetabulum. This may delay the endochondral ossification of the acetabulum.

Volumetric and acetabular changes in the bony pelvis associated with primary closure of classic bladder exstrophy

Repair of classic bladder exstrophy (CBE) is known to alter dimensions of the bony pelvic ring. Pelvic volume and acetabular configuration are additional metrics which merit analysis in the reconstruction process. Advances in magnetic resonance imaging (MRI) allow for precise elucidation of such anatomy in pediatric patients, providing enhanced knowledge of how primary reconstruction may impact factors in pelvic health. An IRB-approved exstrophy-epispadias database of 1337 patients was reviewed for patients with CBE who had pelvic MRI performed before and after repair. Pelvic MRIs were analyzed by a pediatric radiologist, and three-dimensional volumetric renderings of the true pelvis were calculated. Pre- and post-closure imaging were compared, in addition to imaging from age-matched controls without pelvic pathology. Cartilaginous acetabular index and version angles were also calculated and compared between groups. Eighteen patients with post-closure imaging, 14 of whom also had pre-closure imaging, and 23 control patients (ages 0-365 days) were included. The median ages at pre- and post-closure scan were 2 and 178 days, respectively. Osteotomy was performed in 6 (33%) of the closures. The median segmented pelvic volumes were 89cm3 in the pre-closure group, 105cm3 in the post-closure group, and 72cm3 in the control group. At a given age, patients with CBE pre-closure had the largest pelvic volume, and those without bladder exstrophy demonstrated the smallest pelvic volumes (Summary Figure). CBE patients' pelvic volumes were overall lower following repair, relative to age (p=0.007). Cartilaginous acetabular version angle increased following closure, with acetabular orientation converting from retroversion to anteversion in all cases. However, only acetabular version angles were significantly different between groups. This study found that pelvic volume significantly decreased relative to age following primary repair of CBE, but that it did not correct to control levels. Similarly, acetabular retroversion that is naturally seen in exstrophy patients was converted to anteversion post-closure but did not become completely normal. Knowledge of these persistent anatomical anomalies may be useful in treatment of future concerns related to exstrophy, such as continence achievement, pelvic organ prolapse, and potential gait disturbances. Lack of significant differences between study groups regarding acetabular index angles can give assurance to providers that hip dysplasia is neither a natural concern nor iatrogenically inflicted through reconstruction. The primary closure of exstrophy results in pelvic volumes and anteverted acetabula that more closely resemble those without bladder exstrophy, compared to pre-closure findings.

Pathophysiology of Hip Disorders in Patients with Mucopolysaccharidosis IVA.

Patients with mucopolysaccharidoses IVA (MPS IVA) have a progressive accumulation of the specific glycosaminoglycans (GAGs): chondroitin-6-sulfate (C6S) and keratan sulfate (KS), leading to the degeneration of the cartilage matrix and its connective tissue perturbing the regular microarchitecture of cartilage and successively distorting bone ossification and growth. Impaired cartilage quality and poor bone mineralization lead to serious hip disorders in MPS IVA patients. Although hip dysplasia is seen widely in musculoskeletal abnormality of this disorder, the pathophysiology of the hip bone and cartilage morphology in these patients remains unclear. Until now, no systemic study of the hip joints in MPS IVA has been reported by using the combined images of plain film radiographs (PFR) and Magnetic Resonance Imaging (MRI). This study aimed to assess the bony and cartilaginous features of hip joints and to explore the potentially related factors of femoral head osteonecrosis (FHN) and hip subluxation/dislocation in patients with MPS IVA. Hip joints in MPS IVA patients were retrospectively reviewed, based on the findings of PFR and MRI data from 2014 to 2019. Demographic information was also collected and analyzed with imaging measurements. A total of 19 patients (eight boys and 11 girls) were recruited, and 38 hip joints in these patients were examined. Eleven patients (57.9%) had FHN. FHN patients were statistically compared with those without FHN. Correlations between cartilaginous femoral head coverage (CFHC) and acetabular index (AI), cartilaginous AI (CAI), or neck-shaft angle (NSA) were investigated in patients with hip subluxation or dislocation. The greater cartilaginous coverage of the hips than their osseous inherency was observed. Significant correlation was observed between CFHC and AI (r =−0.351, p = 0.049) or CAI (r =−0.381, p = 0.032). Severe subluxations or dislocations were more likely to be present in those with more dysplastic bony and cartilaginous hips. In conclusion, our study provides the first systemic description of bony and cartilaginous characteristics in the hip morphology of MPS IVA patients. We have demonstrated that plain radiography alone leads to a misunderstanding of hip morphology and that MRI measurements with PFR are an essential tool to evaluate the ‘true’ characterization of hips for MPS IVA patients.

Bone maturation of MRI residual developmental dysplasia of the hip with discrepancy between osseous and cartilaginous acetabular index.

Quality of spontaneous amelioration of residual developmental dysplasia of the hip (DDH) is nowadays not possible to predict. Normal age-related values of the osseous acetabular index (OAI), cartilaginous acetabular index and labral acetabular index have been established on MRI. In this study, MRI of dysplastic hips has been evaluated, and further osseous acetabular maturation was followed-up over time on pelvic radiography to find a correlation between MRI findings and radiological evolution. This is a retrospective single-centre study. Children with DDH who had a pelvic MRI between February 2007 and June 2014 were included. AI was measured for osseous (OAI), cartilaginous (cartilaginous acetabular index) and labral (labral acetabular index) values on MRI. OAI was thereafter recorded on each available radiograph during follow-up. A total of 20 hips were included. The mean age at MRI diagnosis was 3.55 years. Two types of DDH were observed: harmonious dysplasia, associated with an osseous and cartilaginous defect (group A, n = 14), and divergent dysplasia, associated with an osseous defect but with sufficient cartilaginous coverage (group B, n = 6). The mean age at final radiological follow-up was 7.6 and 8.3 years (P = 0.7408), respectively. In group A, four (28.6%) children older than 6 years had an OAI of less than 18°, whereas only two (33.3%) children older than 6 years had an OAI less than 18° in group B (P = 0.0117). This study shows that, in one-third of cases, divergent dysplasia leads to a spontaneous recovery. MRI should be used early to accurately diagnose and follow-up DDH cases and allow surgeons to justify the required surgical treatment. Level of Evidence: IV.

Predicting acetabular growth in developmental dysplasia of the hip following open reduction after walking age

BackgroundAcetabular dysplasia of the hip following open reduction can complicate the treatment of developmental dysplasia of the hip (DDH). The purposes of this retrospective study were to investigate the long-term results of open reduction performed via an extensive anterolateral approach for DDH after walking age and to predict acetabular development using postoperative radiographs and arthrograms. MethodsFrom 1973 to 2001, we performed open reduction for 131 hips in 119 pediatric patients with DDH after failed closed reduction. Of these, 85 hips of 73 patients who underwent arthrography at 5 years old were followed-up radiologically until skeletal maturity. Mean age at the time of surgery was 17 ± 4.6 months (range, 10–33 months), and mean age at final survey was 19 ± 5.7 years (range, 14–33 years). Mean follow-up time was 17.7 ± 5.8 years (range, 13–32 years). Groups with satisfactory outcomes (66 hips) and unsatisfactory outcomes (19 hips) according to the Severin classification were compared. Factors predicting acetabular development were identified using univariate and multiple logistic analyses. ResultsUnivariate analysis showed a significant between-group difference in acetabular index (AI) at 2 months postoperatively, and in center-edge (CE) angle, cartilaginous AI (CAI), and cartilaginous CE angle at 5 years old (p < 0.05 each). In multiple logistic regression analysis, CAI at 5 years old represented a predictor of acetabular development after open reduction for DDH (odds ratio, 1.81; 95% confidence interval (CI), 1.04–3.13; p < 0.05). Area under the receiver operating characteristic curve for CAI at 5 years old was 0.93 (95%CI, 0.85–1.0), and the optimal cut-off was 10° (81.8% sensitivity, 92% specificity). ConclusionsA CAI ≥10° on hip arthrograms at 5 years old may offer a useful indicator of the need for corrective surgery following open reduction after walking age.

Hip Morphology in MPS-1H Patients: An MRI-based Study

Hip dysplasia is common in mucopolysaccharidosis type-1H (MPS-1H) patients, but its morphology is not completely understood. No magnetic resonance imaging (MRI)-based studies have been reported in the literature. The purpose of this study was to improve knowledge of hip dysplasia pathology by describing the hip morphology of these patients in MRI scans, plain radiographs, and arthrograms. We performed a retrospective chart review of 18 MPS-1H patients. Supine anteroposterior pelvic radiographs of 36 hips and MRI scans of 18 hips were analyzed. Six arthrographs were also available. Plain radiographs were available for 18 patients. The mean age was 6.0 (SD=3.8) years. The mean acetabular index (AI) was 36.2 degrees (SD=5.8), and the mean migration percentage was 59.0% (SD=17.2). MRI data were available for 9 patients. The MRI findings were compared with the radiographs of the same patient. The mean AI (39.3 degrees, SD=5.8) was confirmed by the MRI findings (39.1 degrees, SD=5.5). The migration percentage was lower in the MRI scans than in the radiographs. Radiologically, the center-edge angle was negative in all patients, with a mean of -16.8 degrees (SD=7.9), and the MRI images produced a more negative value (-19.6 degrees, SD=7.6). The soft tissue coverage of the femoral head was described with the inclusion of the cartilaginous roof and labrum. The cartilaginous AI was 22.4 degrees (SD=7.5), and the labral AI was 13.5 degrees (SD=6.7). All 6 arthrograms revealed stability during dynamic testing. This study provides the first description of hip morphology in MPS-1H patients through MRI-based data. The cartilaginous coverage of the hip was increased compared with that of healthy children. The use of radiography alone may lead to a misunderstanding of hip morphology. MRI and arthrogram is highly recommended if surgery is considered.

Development of the osseous and cartilaginous acetabular index in normal children and those with developmental dysplasia of the hip

The purpose of this study was to investigate the development of the osseous acetabular index (OAI) and cartilaginous acetabular index (CAI) using MRI. The OAI and CAI were measured on the coronal MR images of the hip in 81 children with developmental dysplasia of the hip (DDH), with a mean age of 19.6 months (3 to 70), and 241 normal control children with a mean age of 5.1 years (1 month to 12.5 years). Additionally the developmental patterns of the OAI and CAI in normal children were determined by age-based cross-sectional analysis. Unlike the OAI, the normal CAI decreased rapidly from a mean of 10.17° (sd 1.60) to a mean of 8.25° (sd 1.90) within the first two years of life, and then remained constant at a mean of 8.04° (sd 1.65) until adolescence. Although no difference in OAI was found between the uninvolved hips in children with unilateral DDH and normal hips (p = 0.639), the CAI was significantly different between them both (p < 0.001). The normal CAI has fully formed at birth, and is maintained constantly throughout childhood. The CAI in the unaffected hips in children with unilateral DDH is also mildly dysplastic.

Magnetic Resonance Imaging in Congenital Dysplasia of the Hip

This study was designed to determine the usefulness of magnetic resonance imaging (MRI) in managing congenital hip dysplasia and dislocation. We compared various hip parameters using bony and cartilaginous landmarks. MRI determined that the bony acetabular index (AI) accurately reflects the cartilaginous AI. Bony acetabular indices greater than 30 degrees indicated hip dysplasia, subluxation, or dislocation. MRI demonstrates qualitative information not available on plain films; however, it does not provide further quantitative data, so we do not recommend its routine use in the evaluation of congenital hip dysplasia. The true benefit of MRI may be its ability to identify a group of patients with bone dysplasia but normal cartilaginous growth potential.